Angular Luminance Distribution Research Articles

Quantitative Evaluation of Machined-Surface Gloss Using Visual Simulation and its Application to Sensory Test

In the machining field, the quality of a machined surface is characterized using both quantitative and sensory parameters. It is important to quantitatively evaluate sensory parameters to automate the evaluation of machined surfaces and determine the machining conditions. In this study, we quantitatively evaluate the gloss degree, which is a sensory parameter, via visual simulation. The gloss degree is evaluated based on an angular luminance distribution for machined surfaces cut using different tools. Using the quantitative evaluation result, observation is conducted to predict the appearance of the machined surface, and a sensory test is performed. The result shows that the quantitative evaluation results are consistent with the sensory test results.

Experimental Study of the New Criterion of Lighting Quality Based on Analysis of Luminance Distribution at Moscow Metro Stations

The article presents the experiment in studying a new criterion of lighting quality based on spatial and angular distribution of luminance proposed by the Lighting Engineering sub-department of NIU MPEI. The experiment studies correlation between expert evaluations of lighting quality at 21 stations of the Moscow Metro with analysis based on the criterion of quality of RAW-format luminance photographs of the stations made by means of a camera and adjusted according to luminance measured by a luminance meter. The obtained photos were processed using the proposed criterion. The article presents design of station models and calculations made by means of DIALux software and the programme developed (as part of the work) on the basis of local evaluations. It is demonstrated that the proposed criterion allows us to take account of extended veiling reflections and may be considered as enhancement of the unified glare rating UGR.

35.1: Invited Paper: Measurement and Standardization of Display Lighting Units

Display lighting unit has always been the focus for optimization when comes into display engineering to improve its electrical, optical, and electro‐optical performance. In recent years, with the development of reflective LCD (liquid crystal display), electronic paper display, laser projection display, etc., the measurement of display lighting unit has received more attention. The IEC TC110 "Electronic Display" established the standardization team PT62595 to develop international standards. Currently, the project team has worked a variety of lighting technologies, including back light unit (BLU) and front light unit (FLU), light module and engine, light bar, and light components. In this paper, we reviewed the roadmap of this group and key items that involve in the measurement methods to give an overview of the documents.In the previous year, the IEC released two new standards, IEC62595‐2‐2 “Measuring methods of LED light bars used in LCD BLUs” and IEC62595‐2‐3 “Electro‐optical measuring methods of LED frontlight unit”. Both documents have now been put into the implementation in the display industry.In IEC 6595‐2‐2, spatial luminance uniformity and angular luminance, color uniformity and color angular uniformity were addressed. In Figure 1, it shows an example of a typical light bar luminance distribution profile to indicate the luminance uniformity by quantifying the information along axis.Example of the luminance distribution profiles along the x‐axis, Lv(x, o)figureIn addition, in order to achieve these characteristics, the optical coupling analysis and optimization between the light bar and the light guide plate (LGP) was discussed. Furthermore, this work introduced the specifications on the requirements for test environment, the architecture of the test equipment, the reference diffuser settings, and the coordinate system.In IEC 62595‐2‐3, the standard specifies the measurement conditions and measuring methods for determining electrical, optical, and electro‐optical properties of LED FLUs for reflective displays. In FLU, the light ray of the FLU with a reflective LC display can be sensitive to the testing position and viewing direction. As shown in Figure 2, light rays are introduced to the LGP (light guide plate) from the coupling side. The rays are reflected on the inner surfaces of the micro‐structures (on the front surface) due to TIR (total internal reflection). The FLU is served as a transparent medium that has reflection property on both surfaces. We explained some of the factors that were covered in the standard document for the measurement and evaluation of both surfaces, including angular luminance distribution, luminance uniformity, spectral power distribution, chromaticity uniformity and angular color uniformity in CIE 1976 system, as well as FLU‐polarization characteristics and optical noise (undesired luminance) along the zenith angle in any azimuth angle.Light rays of FLU with a reflective LC displayfigure

Suppression of the color shift of microcavity organic light-emitting diodes through the introduction of a circular polarizer with a nanoporous polymer film

ABSTRACTA circular polarizer (CP) film modified by a nanoporous polymer film (NPF) was applied to improve the viewing angle characteristics of a top-emission organic light-emitting diode (TEOLED) without any serious pixel blur phenomenon. From this approach, the angular color shift (Δu′v′) was significantly improved from 0.096 to 0.056, and the angular luminance distribution was also expanded to the Lambertian distribution direction. The black color had a slightly faded tint, however, like the turn-off condition of the plasma display panel (PDP), regardless of the introduction of NPF below or above the CP. Very interestingly, the surface reflectance of the device with NPF-coated CP was not significantly different from that of the device with non-NPF CP. The pixel blur level according to the distance between the scattering medium and the light source was also investigated. As a result, it was found that the pixel blur phenomenon can be greatly suppressed by applying a thinner encapsulation lid with an NPF film.

Overcoming the efficiency limit of organic light-emitting diodes using ultra-thin and transparent graphene electrodes.

We propose an effective way to enhance the out-coupling efficiencies of organic light-emitting diodes (OLEDs) using graphene as a transparent electrode. In this study, we investigated the detrimental adsorption and internal optics occurring in OLEDs with graphene anodes. The optical out-coupling efficiencies of previous OLEDs with transparent graphene electrodes barely exceeded those of OLEDs with conventional transparent electrodes because of the weak microcavity effect. To overcome this issue, we introduced an internal random scattering layer for light extraction and reduced the optical absorption of the graphene by reducing the number of layers in the multilayered graphene film. The efficiencies of the graphene-OLEDs increased significantly with decreasing the number of graphene layers, strongly indicating absorption reduction. The maximum light extraction efficiency was obtained by using a single-layer graphene electrode together with a scattering layer. As a result, a widened angular luminance distribution with a remarkable external quantum efficiency and a luminous efficacy enhancement of 52.8% and 48.5%, respectively, was achieved. Our approach provides a demonstration of graphene-OLED having a performance comparable to that of conventional OLEDs.

Reshaping the luminance distribution of OLED lighting using optical films

ABSTRACTThe angular distribution of luminance on a combination of a white organic light-emitting diode (OLED) panel and optical films was investigated through an experiment and through optical simulation. Applying an appropriate combination of separate optical films onto the OLED panel provided a great deal of flexibility in shaping the luminance profile of OLED lighting. This was due to the existence of thin air gaps between the OLED and the optical film on it as well as between the optical films, as supported by optical simulation. This flexibility may supply the OLED lighting with an additional degree of freedom, which is effective in adjusting the luminance profile freely.

P-74: Quantum Dot-Enhanced LCDs with Wide Color Gamut and Broad Angular Luminance Distribution

For public displays, wide viewing angle and good sunlight readability are the key requirements. To achieve these goals, we incorporated a quantum dot enhancement film into the LCD backlight unit while eliminating the crossed prism films. The resultant angular luminance distribution is comparable to that of OLED, and the color gamut is enlarged to ~90% of the Rec. 2020 color space. Meanwhile, new LC mixtures are developed to get fast response at wide working temperature range (−40°C ~ 80°C).

Optical outcoupling enhancement in organic light-emitting diodes using a gradually varying refractive index dielectric structure

To provide a practical method to enhance the optical outcoupling of organic light-emitting diodes (OLEDs), we propose the use of a gradual refractive index dielectric (GRID) structure. The GRID structure of the sequentially varying composition ratio was fabricated using a sequential codeposition method. Optical outcoupling from surface plasmon polariton (SPP) modes is promoted owing to the large refractive index of WO3, and the formation of waveguide modes in the GRID structure is impeded owing to the irregular surface morphology of CaF2. The efficiency of the OLEDs was improved by more than 20% using the GRID multicathode OLED (MC-OLED) structure, without requiring an additional patterning process. In addition, the emission spectra remained almost unchanged following the introduction of the GRID MC structures, and the angular distribution of luminance became similar to that of Lambertian emission. Owing to the high performance and simple low-cost fabrication processes, the outcoupling enhancement method using a GRID structure is expected to be a practical solution to improving the luminous efficiency of OLEDs, with applications including high-performance mobile display devices and large-area televisions.

P‐143L: Late‐News Poster: New Characterization of 3D Performance for Multi‐view Autostereoscopic Displays

AbstractIn this study, we presented new concepts defining 3D crosstalk and 3D blur for autostereoscopic displays for multi‐view autostereoscopic displays. First, we measured the angular dependencies of luminance for 9‐view autostereoscopic displays under test patterns of given view and then calculated the 3D crosstalk with the measured luminance profiles. Our new approach gives just a single 3D crosstalk value of similar order to the conventional stereoscopic displays. For the 3D blur, we measured the size of 3D blur of the given 9‐view system with the angular distribution of luminance and a given parallax disparity. From the results, we believe that this new approach is very useful for comparing the 3D crosstalk and 3D blur as 3D performances of various autostereoscopic displays.

55.2: Shaping Arbitrary Angular Luminance Distribution through Directional LGP and Single Inverted‐Concave Lenticular Film for Blue‐Phase LCD‐BLU Hybrid Structure

AbstractA new backlighting optics for shaping a light cone of elliptical cross‐section with an arbitrary eccentricity was studied and realized. The optical structure employs a film with inverted line prism array on the back surface and concave micro‐lenticular lens array on the front surface in combination with a functional light guide featuring with louver prism array on the back surface, and convex lenticular light deflector on the front surface. By varying the radius of the concave lenticular lens on the film the angular luminance distribution can be changed. The variation can be controlled in a wide range in order to obtain light cone cross‐section with different eccentricities. This optical structure was applied to a blue phase LCD‐like structure in which the LCD was sandwiched between the light guide and the film for both illuminating and widening the viewing angle of the display.

A directional backlight with narrow angular luminance distribution for widening the viewing angle for an LCD with a front‐surface light‐scattering film

Abstract— A directional backlight unit has been developed to widen the viewing angle of a TN‐LCD with a front‐surface light‐scattering film/layer. The novel directional backlight has a diagonal of 34 cm and is structured by light‐direction‐control optical micro‐features and an inverted prism film. The backlight has a symmetrical round luminance cone of ±9° and a uniform spatial distribution of 88%. By using this backlight unit in combination with an LCD, the narrow cone resulted in widening of the TN‐LCD's viewing angle up to 120° at full width at half‐maximum.

60.4: Distinguished Paper: A Directional Backlight with Narrow Angular Luminance Distribution for Widening Viewing Angle of a LCD with a Front‐Surface‐Light‐Scattering Film

AbstractA directional backlight unit has been developed for widening the viewing angle of a TN‐LCD with a front‐surface‐light scattering film. The novel directional backlight has a diagonal of 34‐cm and is structured by light‐direction control micro features and an inverted prism film. The backlight has a round luminance cone of +/‐9 deg. and a uniform spatial distribution of 90%. In combination with the LCD, the narrow cone resulted in widening of the TN‐LCD's viewing angle up to 120 deg. FWHM.

직하형 Back Light Unit에 사용하는 변형 막대프리즘의 1차원 배열로 구성한 새로운 BLU 필름

A new sheet of back light unit(BLU) to reduce the number of sheets and enhance the optical performances of direct back light unit(BLU) in a liquid crystal display is proposed and designed. In order to improve the straightness and spatial uniformity of brightness of the BLU, we design the new sheet with linear arrays of complicated bar prism by using the fusion of cylindrical lens and bar prism. Then, we investigate and analyze various optical performances of a BLU including the new sheet through an illumination optical system design program. From these results, we determine the optimum geometrical structure of the sheet. Under the optimum condition, the luminance efficiency and spatial uniformity of luminance of the BLU are 53.5% and 83.5% respectively. And the vertical and horizontal widths of the angular luminance distribution are and respectively. Finally we have fabricated a new BLU sheet according to this design shape by using an ordinary resins.

백라이트 유닛용 V-그루브 도광판의 전산모사 및 DSF성형에 관한 비교연구

Nowadays, TFT-LCD is widely used as display unit of many digital devices. And, the backlight unit(BLU) is used as a light source of TFT-LCD module. In the backlight unit, the most important component is a light guide, which guides the input light to the TFT-LCD module uniformly. Recently, many researchers have focused on improving the efficiency of BLU by changing the design and structure of a light guide. In the present paper, a series of simulation was performed to find the optimal luminance distribution of emanated light from the given geometry as the first step. From the results of simulations for the light guide with given V-groove pattern, the emanated light from it is mostly affected by the groove angle. In the case of acute angle, about 74 degrees was found as optimal angle to satisfy the restrictions of angular luminance distribution, FWHM, the maximum luminance, etc. However, as far as the average luminance value was concerned, the case of 120 degrees(abtuse angle) was found to be the best while prism films were added to the BLU. As a next step the light guide samples of 74 and 120 degrees were manufactured by DSF method, which was recently proposed by the authors. Of course, most of design parameters were chosen by the aid of simulation results. Finally, the results of average luminance values were compared between the simulation and DSF molded samples.

Holographic backlight unit for mobile LCD devices

Abstract— The commercial backlight unit for a portable liquid‐crystal display (LCD) device typically consists of several light‐emitting diodes (LEDs) as the light source, a couple of prismatic sheets and diffusers, and a guide plate for backlight optics. A simplified backlight unit for portable LCDs, merely consisting of a hologram‐imprinted light‐guide plate (H‐LGP) and one diffuser, is proposed in this paper. By employing H‐LGP, it is expected that several optical films essential to the conventional backlight unit can be eliminated. This paper aims to improve the optical efficiency of LGPs by deriving the design parameters of the H‐LGP and performing the related computations. The angular luminance distribution of the emanating light from H‐LGP has been measured and compared with the results obtained by simulation. A proper collimation is necessary in order to increase the luminance. The backlight developed through this work has high optical performance combined with low cost.

Uniform Variable Light Sources for Instrument Calibration

This paper describes light sources that were developed for use in calibrating cameras for space exploration. The design produces a nearly uniform luminance field whose correlated color temperature ranges from 4000 K to 5000 K in the visible. Luminance of the source may be continuously varied by as much as 500:1 without affecting the uniformity of the field. The sources, consisting basically of two integrating cavities with an iris diaphragm interposed, use xenon light. Luminances as high as 25,000 cd m(-2) are possible. Such sources are used for light-transfer calibration, as well as spectral response of camera systems. After a brief theoretical treatment, the design variations are discussed. Measurement data on these sources indicates that the angular luminance distribution approximates a uniform diffuser within a 50-deg cone.